Hitherto, there has been known a silane coupling agent which enhances adhesion between an inorganic material and an organic material. Since the silane coupling agent has a group reactive with an inorganic material and another group reactive with an organic material in one molecule, chemical bonds are formed through the groups to result in enhancing adhesion.
A metal chelate compound is also used for improving compatibility between a resin binder and an inorganic pigment in coating compositions. This compound chemically binds to both an organic material and an inorganic material so as to perform the improvement.
However, in actual usages, neither silane coupling compound nor metal chelate compound is still sufficient in adhesion and compatibility.
On the other hand, there are known tri(trialkylsiloxy)aluminum or a metal chelate/silicon compound as a catalyst for epoxy cationic polymerization. It is generally formulated into a sealing compound for electronic elements. However, it can not be used in a coating composition because it adversely affects storage stability and coating appearance.